Centrifugal compressor for a gas turbine engine



Nov. 29, 1960 D. M. BQRDEN ETAL- 2,962,206 I CENTRIFUGAL COMPRESSOR FORA GAS TURINE ENGINE Filed Sept. 11. 1953 4 Sheets-Sheet 1 IN V EN TORS-174044 M 50 is 72. Samuel ,5; Mllzamsz gwmwwfm Nov. 29, 1960 D. M.BORDEN ETAL 2,962,206 CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE q"&

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CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE Filed Sept. 11, 195: 4Sheets-Sheet s INVENTORS fiat z; M 5 orJe 71, air 727116] 5.144/]:127719.

Nov. 29, 1960 D. M. BORDEN EI'AL 2,962,206

CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE' Filed Sept. 11, 1953 4Sheets-Sheet 4 49 INVENTORS. R Jan '21 M Zariere United States Patent QCENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE David M. Borden,Huntington Woods, and Samuel B. Williams, Birmingham, Mich., assiguorsto Chrysler Corporation, Highland Park, Mich., a corporation of DelawareFiled Sept. 11, 1953, Ser. No. 379,568

Claims. (Cl. 230-119) This invention relates to gasturbine power plantsand more particularly to a centrifugal compressor for use with gasturbine power plants for compressing the'intake air used for combustion.

It is a common practice in the present stage of gas turbine developmentto provide the power plant with an air compressor at a position which isupstream from the burner. The compressor may be either of the positivedisplacement type or of the centrifugal type and it may be powered bymeans of a separate bladed turbine wheel interposed in the high velocitycombustion gases which leave the burner. Suitable coupling means may beused for interconnecting the rotating turbine wheel with the compressor.

The compressor of the present invention includes a bladed fluid inletstructure or inducer which is associated with a rotary compressorelement and which is effective to increase the overall workingefliciency of the compressor unit.

A few of the advantages in increasing the pressure of the air beforecombustion intlude a resulting increase in the density of thecombustible charge, an accompanying increase in the temperature of thecharge which results in increase in the combustion efiiciency, andanimprovement in the distribution characteristics of the charge in theburner.

The present invention includes features which may readily be adapted tobe used with centrifugal compressors and pumps in a variety of differentinstallations. The present disclosure is directed to several forms of acentrifugal compressor in combination with one particular gas turbinepower plant design, but it is not intended that the scope of the presentinvention should be limited to installations of the type hereindisclosed.

An object of the present invention is to provide a centrifugal aircompressor for use with gas turbine power plants or the like, saidcompressor including a bladed air intake portion disposed on theupstream side of the compressor blades.

Another object of the present invention is to provide a bladed rotarycentrifugal air compressor having a means associated therewith forimparting a rotary motion to the intake air while the same is conductedto the bladed portion of the compressor.

Another object of the present invention is to provide a rotarycentrifugal air compressor having an air intake portion which comprisesan axial hub portion, a plurality of stages of radial blades disposedabout the hub and a shroud surrounding the peripheral edges of theblade.

Another object of the present invention is to provide a rotarycentrifugal air compressor having an intake portion disposed on theupstream side thereof for imparting an initial axial acceleration to theintake'air.

Another object of the present invention is to provide a rotarycentrifugal air compressor with a bladed'air intake portion in which theblades thereof are secured to an axial hub by means ofsuitableinsertsformed integrally with the blades which permit the bladesto be readily assembled to the hub.

Another object of the present invention is to provide a centrifugal aircompressor with a bladed air intake portion, as described in thepreceding object, wherein the blades are retained in place and supportedby a peripheral shroud.

Another object of the present invention is to provide a centrifugal aircompressor having a bladed rotor portion with a pair of radial shrouds,a bladed air intake portion on the upstream side of the rotor portion,and a peripheral shroud about the blades in the air intake portion tosupport the same, the peripheral shroud being formed integrally with oneof the pairs of radial rotorshrouds.

Another object of the present invention is to provide a centrifugalcompressor as described in the preceding object in which the peripheralshroud is constructed separately from the radial rotor shroud.

Another object of the present invention is to provide a centrifugal aircompressor having a rotor portion and a bladed air intake portionsdisposed on the upstream side thereof about an axial hub and having aperipheral shroud disposed about the blades, the blades of the airintake'portion being secured to the hub and shroud by means of welding.

Another object of the present invention is to provide a centrifugalcompressor with an air intake portion having a plurality of stages ofradially disposed blades, the angle of pitch for the blades of thesuccessive stages being progressively smaller as the air travelstherethrough.

In general, the compressor of the present invention com prises a rotorelement which is suitably mounted for rotation about its geometric axis.The rotor is provided with an annular opening at the intake end thereoffor the purpose of providing an inlet passageway'forthe intake air. Theair is then conducted axially throughthe rotor within an annularpassageway which is a continuation of the annular opening previouslymentioned. The air then enters the base or mouth of a circular bladedportion of the rotor which extends radially outward from the geometricaxis. The blades in this bladed portion may be radially disposed or maybe formed with entrances or exit angles other than The number of suchblades may be varied as appropriate.

The air is discharged from the bladed portion peripherally in a radialdirection into a diffuser housing which comprises a spiral structure ofprogressively increasing cross sectional area and which is effective toreduce the velocity of the air discharged from the rotor andto convert asubstantial percentage of the air velocity pressure into staticpressure. Such a conversion is necessarily accompanied by an increase inthe air temperature. The path followed by the air throughout thecomponents of the power plant with become obvious from the followingbrief description of the present embodiment with reference to Figure 1of the drawings.

An important feature of the present invention resides in the structurewhich forms the annular passageway extending axially from the inletopening of the rotor to the mouth of the rotor blades. This structurewill be hereinafter referred to as the inducer portion of thecentrifugal compressor.

One or more stages of inducer blades of the airfoil type maybe fixedwithin the inducer passageway in order to impart rotary motion to theaxially moving intake air. Such blading is also effective to increasethe total pressure to a certain extent as the air approachesthe leadingedges of the radial rotor blades.

Such a bladed inducer portion is effective to reduce the'energy lossesdue to sudden changes in the direction of the intake air stream. Alsothe impact losses,-due to unfavorable angles of'attack at the leadingedgeof" 14 to the surrounding atmosphere.

the radial blades, are reduced. Also, energy losses due to excessturbulence and local eddies in the flow pattern are reduced and thetendency of the air stream to break away from the contour of the rotorblades is reduced.

In addition to the above, the bladed inducer portion is effective toincrease the overall pressure ratio since the total pressure at theinlet or leading edge portion of the radial rotor blades is increased.Each of these factors contributes to increase the overall operatingefliciency of the compressor unit.

The blading which is associated with the inducer portion of the rotor isdisposed in the disclosed embodiments of the invention in two axiallyspaced stages about the geometric axis. Suitable means are provided formounting the individual inducer blades which permit them to be readilyassembled on a production basis. Further, an inducer shroud is providedwhich surrounds the outer peripheral edges of the inducer blades for thepurpose of adding support to the blades and for defining the axiallyextending inducer passageway.

The various disclosed embodiments will be described in more particulardetail with reference to the accompanying drawings wherein:

Figure 1 is a cross sectional view of a gas turbine power plant of theautomotive type which incorporates one form of the compressor of thepresent invention;

Figure 1A is an enlarged subassembly view of the centrifugal compressorof Figure 1;

Figure 2 is a sectional view of one embodiment of the compressor rotorshowing the bladed inducer portion;

Figure 3 is a detail sectional view showing the welded bladeconstruction of a second form of the compressor of the presentinvention;

Figure 4 is a sectional view of the structure shown in Figure 2 and istaken along the section line 44 of Figure 3;

Figure 5 is a cross sectional view of a third form of the presentinvention;

Figure 5A is a detail elevation view of the inducer blade adapted forassembly in the structure shown in Figure 5;

Figure 6 is a cross sectional view of a fourth form of the presentinvention;

Figure 6A is a detail elevation view of an inducer blade adapted forassembly in the structure shown in Figure 6.

Having reference first to the gas turbine assembly view of Figure 1, thecompressor unit is shown generally by means of numeral 10 and itcomprises the bladed inducer portion, shown at 11, and the rotor portion12 in adjacent relationship with respect to each other.

. The air intake means for the gas turbine power plant includes anintake housing 13 having an intake opening The outer portion of thehousing 13 partly defines an annular passageway 15 which extendsradially inward from the opening 14. The cross sectional shape of thepassageway 15, as seen in Figure l, is that of a funneled configurationthe center line of which forms a reverse curve. The passageway 15terminates in an axially extending annular conduit structure, shown at16, near the geometric axis of the housing 13.

The inducer portion 11 defines an annular space about the hub 17 of thecompressor rotor 10, said annular space forming a continuation of theconduit structure 16.

The hub 17 extends outwardly through the central axis of the housing 13and is positively connected to an accessory drive shown generally at 18.Suitable bearing means are provided in the housing structure 13 toprovide end support for the rotor and inducer.

The inducer portion 11 of the compressor unitltl is sealed by suitablesealing means formed in the structure 16 and the hub 17 may be providedwith a similar type of sealing means 20. The rotor portion 12 of thecompressor unit 10 is adapted to discharge the intake air radiallythrough bladed passages formed therein into an 4 annular inlet opening19 in a diffuser structure shown generally at 21.

The diffuser 21 comprises a volute-shaped housing, which forms a part ofthe gas turbine housing proper. The volute housing has a cross sectionalarea which becomes progressively greater as'the air discharged from therotor portion 12 travels therethrough.

After the air completes substantially a 360 degree turn in the diffuser21, the static pressure thereof is increased. This high pressure air iscollected in the regenerator housing portion 22 and from there it isallowed to pass through a section of a rotary regenerator shown at 23.

The rotary regenerator 23 is rotatably mounted at 24 and is providedwith suitable axially extending passages through which the compressedair is allowed to pass into the annular chamber designated by means ofthe numeral 25.

The chamber 25 is defined by the gas turbine outer wall structure 26 andthe circular baffle structure 27 disposed internally of the wallstructure 26.

The air is then passed under pressure from the chamber 25 into a burner,not shown. A suitable means is associated within the burner for mixingfuel with the compressed air and for igniting the mixture. The burnedgases then pass from the burner into the chamber designated in Figure 1by means of numeral 28.

The chamber 28 is annular in shape and is defined by the baffiestructure 27 and by another bafiie 29 disposed within the structure 27.The direction of motion of the expanded and heated combustion gasespassing from the burner is such that they pass through the chamber 28 ina spiral path. The cross sectional area of the chamber 28 progressivelydecreases as it progresses about the axis of the engine. The expandedcombustion gases pass from the chamber 28 and enter an annular space 30defined by turbine housing structure 31 and the bafiie structure 29.

A cascade of stator blades 33 is disposed about the axis of the engineWithin the annular space 30. The blades 33 are succeeded by an annularcascade of primary turbine blades 34 disposed within space 30 upon theperiphery of turbine wheel 35.

A second cascade of stator blades is mounted as shown at 36 adjacent theblades 34 and these are followed by the secondary turbine blades 37mounted about the periphery of the secondary turbine wheel 38.

The gases which are exhausted from the turbine blades 37 are allowed topass into a chamber designated by means 24 thereby permitting the heatedsection of the regenerator to come in contact with the relatively coolerair passing into the burner and also permitting the cooler sectionsthereof to come in contact with the hot exhaust gases being exhaustedfrom the engine.

The turbine wheel 38 is provided with a shaft which is drivablyconnected to the input pinion of a reduction gear box shown generally bymeans of numeral 42. The output gear of the reduction gear box 42 isconnected to the output shaft 43 from which useful power may beobtained.

The primary turbine wheel 35 is formed with a central shaft 44 which isdrivably secured to the hub member 17 of the compressor unit 10. Thehigh velocity gases passing through the annular space 30 are effectiveto drive aaeaaoa '5 unitis shown in more particular detail. The shaft 44carries at one end thereof the turbine wheel 35. The other end of shaft44 is threa'dably'secured at 65 within the hub member 17. The hub member17 is disposed in abutting relationship with one end of a hub member 61for the rotor portion 12.

An adaptor 53, which maybe substantially cylindrical in shape, isdisposed coaxially about shaft 44 in abutting relationship with theother side of the rotor hub member 53. The adaptor 61 is formed with anextension 62 upon which a suitable bearing and sealing structure may beassembled.

The shaft 44 is effective to maintain the turbine wheel 35, the adaptor53, the rotor 12 and the hub member 17 in axially stacked relationship.

The rotor 12 includes a circular row of blades 45 disposed about theaxial shaft 44 and between a pair of blade shrouds 48 and 49. The innerperiphery of shroud 48 is assembled at 55 to a cylindrical inducershroud shown at 58, by any suitable means. For example, the shrouds 58and 48 may be brazed together'or they may be assembled by means of aforce fit.

The annular passageway defined by the inducer shroud 58 and hub 17 hasdisposed therein a pair of blade stages shown by means of members 73 and72. The blades may be secured to the hub 17 by means of integral inserts76 formed at the blade roots. The inserts are adapted to fit withinsuitable slots in the hub 17.

The projected angle formed by the principal axis of the blade slots andthe axis of the shaft 44 may be varied for each stage as appropriate. Itis preferable to form the blade slots so that the direction of thechordal lines for the successive blade stages will progressivelyapproach the axial direction defined by the rotor axis. If desired, theblade angles of the successive stages 73 and 72 may be progressivelyvaried so that the blade exit angle for the last stage is substantiallyequal to the entranceangle for the rotor blades 45.

Having reference next to Figure 2, another form of the compressor unitis shown in more particular detail and is generally designated-by meansof numeral 110. The rotor 112 thereof is shown extending radiallyoutward and it includes a circular row of blades 145 formingtherebetween channels which originate at the leading edges 146 of theblades 145 and which terminate at the tip edges 147 at the outerperipheral edge. The blades 145 are enclosed by the shroud structures143 and 149.

The rotor 112 is centrally apertured at 151 to receive the shaft 44.Suitable means may be provided for securing the rotor 112 to the shaft44, such as the pins 152 secured to the shoulder piece 153. The rotorstructure comprising shrouds, 148 and 149, and the blades 145 may becast as an integral unit.

The rotor 112 is provided with a shoulder 154 against which aninducershroud member is abutted. The shroud member includes a centrallyapertured hub portion 155 which receives the shaft 44 therethrough andupon which a circular cascade of blades 156 is radially disposed. Theblades 156 are adapted to mate with the leading edges 146 of the blades145 thereby forming one continuous blade structure from the leadingedges 157 of the blades 156 to the tip edge 147 of the blades 145.

An inducer shroud 158 is formed integrally with the blades 156 and itextends axially from the tip edges of the blades 156. The shroud 158,blades 156 and the hub 155 may be cast as one integral unit.

The hub 155 has formed thereon a shoulder surface 159 against which asecondary stage bladed assembly of the inducer 111 is positioned. Thissecondary stage assembly includes a hub 161which is also centrally boredat 162 to receive the shaft 44. The hub 161 is counterbored at 163 toreceive therein an extension 164 of a hub 165 which is associated with aprimary stage bladed assembly of the inducer 111. The hub 165 is alsocounterbored at 166 and it receives therewithin a holding adaptor 167which may be splinedt at. 168 upon. the shaft-44 and is efiective tohold the members 165, 161,155 and the rotor 112 in a fixed axialposition. A suitable snap ring may be provided as shown at 167' toprevent axialmovement of the bladedassembly.

The hubs 161-and are each provided Witha circular row of slots shown bymeans of dotted lines at 169 and 170 respectively. Within these slotsarereceived, respectively, a rowof secondary stage inducer blades 172 and arow of primary stage inducer blades 173.

The inducer blades 172 and 173 are each provided with suitable baseportions which are adapted to fit into the associated slots in themembers 161. and 165. The extension 164 in the hub member 165 serves asaradial spacer for the blades 172 and the adaptor 167 serves as a radialspacer for the blades 173.-

The slots 169 and 17 0-may be formed at various angular positions withrespect to the axis of thecompressor 110 in order to suitably positionthe associated inducer blades.

The shroud 158 is adapted to extend over the outer tip edges of theinducer blades in order to provide a means of support for. thebladesandto define a suitable axial annular inducer passageway. The inducer158 has formed thereon two rows of holes adapted to. receive 7 pins 174which maybe formed. onthe inducer blades 172 and 173 to provideadditional blade support.

A key 175 is received within suitable key slots formed in shaft 44-andhubs 155,161, and165 for the purpose of preventing rotation of the rubmembers upon shaft 44.

Figures 3 and 4 illustrate a modified inducer shroud assembly. The hub155 shown in Figures 3 and 4 corresponds to'hub 155 shown inFigure 2 andthe blades 156' correspond to blades 156 of Figure 2. The blades, asshown'in Figures 3 and 4,. are secured to the hub 155 by means of weldmetal '176.

The inducer shroud is shown in Figures 3- and 4 at 158 and itcomprises aseparatemember which is slotted at 177 to receive the tip edge of blades156'. The blades 156' maybe welded to.the shroud as-shown at 178.

.Referringnext to Figure 5, another modified form of the invention isillustrated. The rotor portion 212 of the compressor unit .210. ofFigure S includes a radial shroud 249 and integrallyformed rotor blades245. Only one. radial shroud-isprovided in this embodiment of theinvention, the pump stationary housing serving to perform the functionofa secondshroud.

A first hub member is shown at 255 uponwhich the radial blades256 areradially secured. The blades 256 are adapted-to meet the leadingedges246 of the blades 245 and to form extensions of the blades 245'. t

The inducer shroud 210 is integrally secured to the tip edges of theblades 256. The assembly consisting of shroud 210, blade 256 and hub 255corresponds to the shroud 158, blades 156, and hub 155 of the assembly"of Figure 2. r

The hub members for the second and first stages of the inducer are shownat 261 and 265 respectively. Each of the hubs 261 and 265 are providedwith slots shown in Figure 5 at 269 and 270, respectively, withinwhichtthe inducer blades are disposed. The hubs 255, 261, and 265 areheld in a fixed axial position by the nut 267 threaded at 268 upon theshaft 44.

The inducer blades are shown in Figure 5 at,272 and 273. Figure 5A is adetail view of one of the blades which include a base portion 271 havingfore and aft extensions thereon to: provide added. blade support. Thebase 271 of each blade is adapted to fit into the associated slots 269and 270. Axial displacement of the blades 272 and 273 ispreventedbymeans of the abutting relationship of the ends of the base portion271-with the adjacent hub 255 and the nut 267. Radial displacement ofthe blades 272 and 273 is preventedby the shroud '210 which surroundsthe blades and contacts the tip edges thereof. If desired, suitablepinsor other supporting means may be provided to secure thcblades 272and 273 7 to the shroud 210 to provide added support to withstandbending loads.

Referring next to Figure 6, another modified form of the compressor unitis illustrated. The rotor portion of the unit is shown at 312 and itcomprises a shroud 349, radial blades 345 and a second shroud 348. Theinducer shroud is shown at 358 and is formed integrally with the rotorshroud 348. The rotor 312 and the shroud 358 may be cast in one piece asan integral unit.

The inducer portion, shown at 311, comprises a hub member 365 which hasan axially extending portion 361 formed thereon. The hub 365 is retainedupon shaft 44 by the threaded engagement shown at 368.

The secondary stage and primary stage inducer blades are shown at 372and 373 respectively. One of the blades is illustrated in detail inFigure 6A. It is seen that each of the blades is provided with a baseportion which is formed with a tongue 371 having a projection 360extending therefrom. Mating slots are provided in the hub 365 and theextension 361 to receive the tongues 371 and projections 360 on theassociated inducer blades. Radial displacement of the inducer blades isprevented by the shroud 358 which contacts the tip edge of each of theblades.

It should be noted from the various views of the inducer portions, andespecially from Figures A and 6A, that the blades are shaped to providean air foil having sections of increasing chordal length as the radialdistance of the respective sections from the central axis increases. Inother words, the chordal length of any one section from the root to thetip edge is substantially directly proportional to the radial distanceof that section to the axis. Such a configuration is considereddesirable because the aerodynamic characteristics of the blades are suchthat the efficiency is higher if the ratio of the chordal length at anyone radius to the spacing between the blades at that same radius is keptconstant. This ratio is known as the solidityratio.

Further, the need for a diverging chordal length for the inducer bladesmay become apparent when it is observed that in order to maintain auniform angular velocity of the inlet air stream through the inducershroud, the linear tangential velocity of a particle of air at anyradial position must be proportional to the radial distance of thatparticle from the axis of rotation. Therefore, it is apparent that theparticles of air near the outer tip edge of the inducer blades must beaccelerated over a longer period of time than the particles of airnearer the axis of rotation in order to maintain a uniform angularvelocity. By providing the blade near the outer edge with a longerchordal length than that of the portion of the blade radially inward,the air near the tip edge is so acted upon for a relatively longerperiod of time.

The blades may also be provided with a variable double camber crosssectional shape as shown in Figures 5A and 6A. The blunt nose leadingedges and the relatively thin trailing edges of the blades may also beprovided with appropriate entrance and exit angles, respectively, inorder to obtain optimum performance.

The composition of the cast structure of the various compressor unitsherein disclosed may be of aluminum or magnesium, or alloys thereof, inorder to reduce the total Weight. The inducer blades may be formed, ifdesired, of a suitable plastic such as Bakelite in order to reducemanufacturing costs and to acilitate the blade forming process.

The blade support which is provided by the various inducer shroudscontributes to the vibrational stability of the assembly and preventsfatigue failures at the blade roots.

It is contemplated that the present invention may be used in kineticmachinery which makesuse of or which acts upon fluids other than air orgases. The device of the present invention may, for example, be readilyadapted to be used with centrifugal machines employing liquids such aswater, liquid fuel, or the like.

The number of inducer blade stages may be varied as appropriate and alsothe entrance and exit angles of the blades may be varied. It ispreferably to provide the blades of the successive inducer stages withprogressively varying entrance angles which approach in value themagnitude of the entrance angle of the rotor blades.

The inducer blades may also be of the single camber type or the zerocamber type if such a design is desired. Such blades might well be usedon low capacity units without an appreciable loss in operatingefiiciency.

While various embodiments of the invention have been disclosed, it isunderstood that the invention is not limited thereto since manyvariations may readily become apparent to those skilled in the art, andthe invention is to be given its broadest possible interpretation withinthe scope of the following claims.

We claim:

1. In combination, a high speed rotor for a gas turbine engine, an aircompressor including a central rotatable hub coaxial with said rotor anddriven thereby, at least one annular outer one-piece shroud coaxial withsaid hub, a plurality of generally radially extending blades, each bladehaving a root portion at its radially inner end, key and socket means soconstructed and arranged between said inner end and hub as to preventrelative axial and angular movement of said blade with respect to saidhub and so that said blade is freely shiftable radially with respect tosaid hub, the diameter of the inner periphery of said shroud beingsubstantially equal to twice the distance from the tip of said blade tothe axis of said hub when the blade, shroud, and hub are in unstressedand assembled condition prior to rotation thereof, so that forcedengagement between said shroud and the radially outer end of the bladeunder the infiuence of centrifugal force during high speed operation ofsaid compressor takes place, said shroud closely encircling the radiallyouter ends of said blades and providing radial support for said outerends when said blades are forced outwardly against said shroud bycentrifugal force during said operation.

2. The combination according to claim 1 and comprising in addition meansinterconnecting said shroud and the radially outer ends of said blades.

3. The combination as in claim 1 wherein said key and socket meansincludes a generally radially opening socket in said hub mating with oneof each of said root portion, the root portion of each blade comprisingan out-of-round tongue and a narrow finger of the radially inner end ofthe tongue, said tongue and finger extending radially inwardly andseating snugly within the mating socket therefor.

4. The combination according to claim 3 wherein said tongue iscompartively thin and said finger is of reduced width with respect tothe width of said tongue.

5. In combination, a high speed rotor for a gas turbine engine, an aircompressor comprising a compressor rotor having a central rotor hub andan annular rotor shroud coaxial with said hub and spaced radiallytherefrom to define an annular rotor passageway, an inducer hubrotatable coaxially with said rotor hub, at least one annular one-pieceinducer shroud distinct from said rotor shroud, said inducer shroudbeing coaxial with said inducer hub and spaced radially therefrom at theupstream end of said rotor shroud to define an annular inducerpassageway in communication with said rotor passageway, the rotor andinducer hubs being rotatable coaxially with said engine rotor and beingdriven thereby, a plurality of generally radially extending inducerblades, each blade having a root portion at its radially inner end, keyand socket means so constructed and arranged between said inner end andinducer hub as to prevent relative axial and angular movement of saidblade with respect to said inducer hub and so that said blade is freelyshiftable radially with respect to said inducer hub, the diameter of theinner periphery of said inducer shroud being substantially equal totwice the distance from the tip of said blade to the axis of saidinducer hub when the blade, inducer shroud, and inducer hub are inunstressed and assembled condition prior to rotation thereof, so thatforced engagement between said inducer shroud and the radially outer endof the blade under the influence of centrifugal force during high speedoperation of said compressor takes place, said inducer shroud closelyencircling the radially outer ends of said blades and providing radialsupport for said outer ends when said blades are forced outwardlyagainst said inducer shroud by centrifugal force during said operation.

References Cited in the file of this patent UNITED STATES PATENTS953,526 Green Mar. 29, 1910 10 Havill Oct. 8, 1935 Szydlowski Aug. 6,1940 Werther Dec. 8, 1942 Rockwell et al Mar. 30, 1948 Miller June 19,1951 Szczeniowski Oct. 2, 1951 Jonker Sept. 2, 1952 Lysholm Dec. 2, 1952Klein Nov. 24, 1953 Travers Oct. 19, 1954 Jandasek Dec. 7, 1954 Zeidleret al Dec. 15, 1959 FOREIGN PATENTS Austria May 26, 1924 Germany Jan.29, 1941 Great Britain Apr. 1, 1936 Great Britain July 9, 1947 ItalyIan. 14, 1939 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTIONPatent NO. 2,962,206 Novembr 29, 1960 David M. Borden et al.

pears in the above numbered pat- Itis hereby certified that error ap dLetters Patent should read as ent requiring correction and that the saicorrected below.

Column 2, line 20, for "portions" read portion 53, for "with". read willcolumn 4, line 53, for "the" read this column 6, line 29, for "rub' readhub column 8, line 5, for "preferably" read preferable line 50, for "ofthe" read on the Signed and sealed this 6th day of June 1961. ii

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents

